So when they "retired" were they actually just trying to get out of their contract with (I think) Gleam?
When I used to work through an agency back in the day I tried to leave and go to another one which paid higher salary for the same job, but they told me as they had clients in common with my old one they could get done for "poaching" me under competition law, and if I wanted to interview with them I had to leave my current agency and wait for an extended period of time, I can't remember it was either 6 months or a year, then go back and apply to them.
Sounds like a similar situation here.